Process and apparatus for producing a substantially neutral electric atmosphere



13, 1966 J w. MICHENER ETAL 3,292,042

PROCESS AND APl ARATUs FOR PRODUCING A SUBSTANTIALLY NEUTRAL ELECTRICATMOSPHERE Filed June 10, 1 963 5 Sheets-Sheet 2 O 0 R I l O O 01 l O 06 o LL| w I o o" "3 A A o I I (no O j (9 O 0 6 r I v O O N l O I I I l lI O O O 8 (G O L0 01 28 8 Q K0 0 no I m m 'O'Q/SNOI NI NOLLVELLNBONOOINVENTORS JOHN w. MICHENER BY JIMMY L.QUINN ATTORNEY 1 1966 J w MICHENERETAL 3,

PROCESS AND APP ARA IUS FOR PRODUCING A SUBSTANTIALLY NEUTRAL ELECTRICATMOSPHERE Filed June 10, 1963 5 Sheets-Sheet I5 m w 90% if 0 I 2 o m 06 /o o I 3. m w 70 0: UJ F- 2 60% O O O o z E m I; u.|

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INVENTORS JOHN W. MICHENER BY JIMMY L.QU|NN ATTORNEY United StatesPatent PROCESS AND APPARATUS FOR PRODUCING A SUBSTANTIALLY NEUTRALELECTRIC ATMOS- PHERE John W. Michener and Jimmy L. Quinn, Spartanhurg,

S.C., assignors to Deering Milliken Research Corporation, Spartanburg,S.C., a corporation of Delaware Filed June 10, 1963, Ser. No. 286,633 12Claims. (Cl. 3172) This invention relates to method and apparatus forimproving the performing of operations on materials which are influencedby electrically charged bodies. More specifically this invention relatesto a method and apparatus for producing a substantially neutral electricatmosphere or an atmosphere of reduced electric charge whereby materialswhich are influenced by electrically charged bodies may be processedwith a minimum of interference.

In the handling of materials which are subject to infiuence byelectrically charged bodies such as textile fibers, fine powders, thinfilms or, in general, objects which have relatively small mass, variousefforts have been made to overcome the effects of electrically chargedbodies, these efforts being concentrated for the most part in increasingthe humidity of the atmosphere and in ionic emissive static eliminators.Increasing the humidity of the atmosphere has the effect of increasingthe amount of moisture on the low mass objects, that is to say fibers,particles or films being treated. The high moisture content willincrease the electrical conductivity of the low mass objects and therebyserve to eliminate some of the electrostatic effects. High moisture may,however, produce a tackiness in the objects being processed and willthereby interfere with processing. The increase in the moisture in theatmosphere also has the effect of decreasing atmospheric conductivity byreducing ionic mobility and may also produce an increase in the netspace charge. An increase in the net space charge will, pf course,produce more charging in low mass objects exposed to such an atmosphere.The ion emmissive static eliminators are of two general types which arethe radioactive source type and the high voltage discharge type. Both ofthese types of ion emitting static eliminators function by being placedin close proximity with an object having a static charge. The staticeliminator neutralizes this static charge by emitting large numbers ofions so that ions of proper polarity are attracted to the charged objectand thereby neutralize it. Static eliminators, however, while effectivein eliminating static effects which are due to surface friction are notsatisfactory in the elimination of space charges which give rise tostatic troubles in low mass objects which are being processed.

It is therefore an object of this invention to provide a method andapparatus for overcoming space charges in the vicinity of low massarticles which are being processed.

It is another object of this invention to provide a method for improvingthe handling of fibrous materials subject to the influence ofelectrically charged bodies.

It is still another object of this invention to provide an apparatus forthe annihilation or reduction of space charges in the atmospheressurrounding low mass articles which are being processed.

In accordance with this invention, it has now been discovered thatatmospheric ionization in production areas may be controlled by placinga charged grid in the main air stream of an air circulating systemwhereby charged particles contained in the air stream are annihilatedupon approaching and being deflected to the grid carrying an oppositecharge. It should be understood that the grid is any device which iscapable of carrying a high voltage j charge and that the circulating airsystem is any system which has the ability to provide a significant airexchange in the atmosphere surrounding a production area. The

charge placed on the grid may be an alternating current charge or adirect current charge. Whether alternating current or direct current isemployed, the charge should be great enough to annihilate atmosphericions, but not so great as to generate ions, that is to say not so greatas to become an ion discharge device. The alternating current chargedgrid will always remove those charged ions which are present in apreponderance as the grid will function as a positive grid for one timeinterval and/ or a negative grid for another time interval. Thepreferred current for purposes of this invention is direct current of apolarity which is determined by an ion measuring device. A typicalinstallation consists of a charged grid placed in the air conditioningduct of a production area, the grid comprising a row of parallel copperWires with about a one-inch spacing between wires. The wires are mountedon an insulated. support and are usually operated with direct current ofpreselected polarity and preselected voltage in the range of from about2,000 volts to about 30,000 volts, the voltage being set so that thereturn air contains a very low space charge. The charged grid willattract and annihilate ions with a charge opposite to that of the Wiregrid. It is generally not necessary or even desirable to annihilate allof the negative ions, should these be the type of ions being removed,since a small excess of positive ions is usually produced in theproduction areas which are then neutralized by the negative ions cominginto the room. In this way, the space charge in the room is made quitelow. Due to normal variations in the rate of ion production and in theair circulation, the voltage required on the grid in order to maintain aminimum space charge may vary considerably. Where the air circulationsystem is something other than an air conditioning unit such as forinstance a window fan circulation system, the space charge of the airbeing circulated may be positive rather than negatively charged as isusually the case in a water Washed air conditioning unit. For thesereasons a control system is desirable, the control system being employedto govern the voltage as well as the polarity employed on the grid. Abetter understanding of the invention may be had from the drawings whichare as follows:

FIGURE 1 is a circuit diagram of one form of ion annihilation system ofthis invention.

FIGURE 2 is a circuit diagram of another form of ion annihilation systemof this invention.

FIGURE 3 is a chart plotting ion concentration against grid voltage.

FIGURE 4 is a chart illustrating weaving efficiency.

FIGURE 5 is a chart illustrating comber efficiency.

In FIGURE 1, a grid which is in the air flow of an air circulatingdevice is placed in circuit with a high voltage power supply which maybe either a direct current power supply or an alternating current powersupply. The voltage is regulated by an automatic control system whichfunctions in response to a space charge measuring instrument. If sodesired, a recorder may be placed in circuit with the space chargemeasuring instrument.

A somewhat more complex ion annihilation system is set forth in FIGURE2, wherein a grid which is in the air flow of an air circulating deviceis placed in circuit with a high voltage direct current power supply.The high voltage power supply is regulated by a signal from a spacecharge measuring instrument. The space charge measuring instrument is adifferential ion counter which functions by drawing a metered volume ofionized air through a collector tube by a suction blower. The ions arethen trapped by a collecting electrode wherein the charges aretransferred to a highly sensitive electrometer. The measured spacecharge from the differential ion counter is then recorded by a clampingtype recorder. When the recorder which is periodically actuated by atiming mechanism reaches an instantaneous preselected ion count value,it places a motor in circuit which turns a variable transformer which isin circuit with the high voltage power supply, thereby increasing ordecreasing the voltage supplied to the grid. When the recorder reaches apreselected minimum ion value it will also reverse the polarity of thehigh voltage power supply, thus permitting the annihilation of ions ofanother charge.

FIGURE 3 of the drawings is a chart plotting negative ion concentrationsagainst direct current grid voltage of positive polarity. The grid is astraight wire grid spaced /2 inch and employing a wire diameter of .1055inch. While the chart plots negative ion concentration, it should beunderstood that the same relationship exists between positive ionconcentration and direct current voltage of negative polarity. It isnoticeable from the diagram that while even low grid voltages willprovide a significant reduction in ion concentration that the eificiencyof the system increases as the voltage is raised to maximum values. Itis diflicult, however, to define optimum voltages for operation of theapparatus and process of this invention as optimum conditions will varywith the type of grid being employed, the air velocity, and the mass orphysical dimensions of the ionic material present in the atmosphere.Examples of optimum voltages for certain specific conditions are asfollows:

Straight wire grid spaced /2" Wire diameter, .1055 in.

Air velocity over grid, 690 ft./min. Voltage, 14 kv.

Screen wire grid spaced /2" Wire diameter, 3/64 Air velocity over grid,2,000 ft./min. Voltage, 18,000 volts It is important to understand thedistinction existing between a space charge due to atmosphericionization and a static charge existing on an object. The atmospherenormally contains at least a small number of ionized particles. Theseparticles may be ionized atoms or they may be bits of dust or dropletsof water which are charged or ionized. Any of these charges are producednaturally by interaction with cosmic rays, the breakup of Water dropletsinto fine particles some with a positive charge and some with a negativecharge, electrical discharge by friction against a surface and by airturbulence. These naturally produced ionized particles along withcertain artificially produced ionized particles in the atmosphereconstitute atmospheric ionization. External atmospheric air normally hasa few ionized particles that is to say a number in the range of from toabout 1000 ions per cubic centimeter of air. When this average number ofions is greatly increased there is usually a great excess of eitherpositive or negative ions since, if there is a large number of both, thepositive and negative ions will be attracted to each other resulting inuncharged particles. The net excess of positive or negative ions issometimes referred to as net space charge.

Atmospheric ionization has a detrimental influence on the processing oflow mass objects such as textile fibers, films, fine powders and thelike, by bombarding these low mass articles with ions and therebycausing the articles to become charged. As certain of these articlesbecome charged they will repel one another since most will have the samecharge polarity while at the same time some of these charged articleswill become attracted to uncharged surfaces. In textile processing offibers, those fibers which have become charged with like charges Willexhibit repulsive forces between themselves and at the same time exhibitan attraction toward uncharged surfaces. Such repulsive and attractiveforces will cause a fibrous strand to become wild, that is to say, tobecome uncontrollable and of nonuniform density and thereby increase theprobability of a process interruption.

Week Percent ends down Space charge Excess concentration of totalspindles negative ions per cc.

1 Yarn Breakage.

The data of the table was obtained from the spinning of a 65% polyester,35% cotton blend yarn in a spinning room employing a water washed airconditioning system. The voltage on the grid was raised with eachsucceeding week, thereby reducing the space charge and correspondinglythe concentration of ions per cubic centimeter, and resulting in areduction of percent ends down/total spindles. The space charge is anarbitrary meter reading which may be correlated to concentration of ionsper cc. A 1.0 reading in space charge is equal to 12,500 ions per cc.

An illustration of the improvement obtained in the weaving of textilesis given in the chart set forth in FIG- URE 4. The chart plots percentweaving efficiency which is number of actual picks number of possiblepicks readily be seen that a marked improvement in weaving efficiency isobtained when the ion annihilation system of this invention is employedin a weaving zone.

An illustration of the improvement obtained in the combing of textilesis given in the chart set forth in FIG- URE 5. The chart plots comberefficiency and space charge (1 unit space charge being equal to 12,500ions/ cc.) against periodic time intervals of measurement. The spacecharge is illustrated by means of a broken line, while comber efiiciencyis illustrated by means of a solid line. It may be readily seen thatcomber efiiciency increases as space charge decreases.

What is claimed is:

1. The method of improving the processing of low mass articles which aresubject to attraction and displacement by electrically charged bodiescomprising circulating ion containing atmosphere in the vicinity of saidlow mass articles in a manner so as to contact an oppositely chargedmember which carries a charge suificient to annihilate atmospheric ionsbut insufficient to generate ions thereby annihilating-those ions whichwere previously contained within said atmosphere whereby bodies will notacquire an electrical charge such as to subject low mass articles toattraction and displacement by said electrically charged bodies.

2. The method of claim 1 wherein said member is charged with a directcurrent charge.

3. The method of claim 1 wherein said low mass arti cles are textilefibers.

4. The method of improving the processing of low mass articles in anarea having an air supply system for recirculation of air throughout thearea, said method comprising generating in the air for recirculation anelectric field sufiicient to attract ions of a given polarity saidelectric field being produced by a voltage of sufficient intensity toannihilate atmospheric ions Ibut insufficient to generate ions andpassing air through said electric field thereby permitting ions of saidgiven polarity to be attracted to and be annihilated in the presence ofsaid electric field and thereafter passing the thus treated air throughsaid area.

5. The method of claim 4 wherein said electric field is a fieldgenerated by direct current.

6. The method of claim 4 wherein said low mass articles are textilefibers.

7. The method of aiding in the processing of textile fiber materials ina textile processing room comprising generating an electric field in theion containing air for said room of sufficient strength to attract andannihilate ions in substantial numbers but insufiicient to generate ionsand circulating said air through said electric field.

8. The method of claim 7 wherein said electric field is an electricfield generated by direct current.

9. An apparatus for the annihilation of atmospheric ions comprising agrid member, a high voltage source in circuit with said grid member, thepolarity and voltage of said high voltage source being controlled by apolarity and voltage regulator which functions in response to adifferential ion counter by causing a polarity opposite that indicatedby said differential ion counter to be applied to said grid member at avoltage insuflicient to generate ionic material and an air circulatingsystem suitable for continuously passing air over said grid members.

10. The apparatus of claim 9 wherein said air circulating system is anair conditioning unit.

11. An apparatus for the annihilation of atmospheric ions comprising agrid member, an air circulating system suitable for continuously passingair over said grid member, a high voltage source in circuit with saidgrid member, the polarity and voltage of said high voltage source beingcontrolled by a polarity and voltage regulator which functions inresponse to a differential ion counter by causing a polarity oppositethat indicated by said diiferential ion counter to be applied to saidgrid member at a voltage insuflicient to generate ionic material, saiddifferential ion counter being in circuit with a clamping type recordingunit.

12. The apparatus of claim 11 wherein said air circulating system is anair conditioning unit.

References Cited by the Examiner UNITED STATES PATENTS 844,300 2/ 1907Chapman 3 l72 X 1,992,974 3/1935 Thompson 3l5111 X 2,462,890 3/ 1949Newman 250 X 3,035,208 5/1962 Clark 3l72 X OTHER REFERENCES 376,930,Peycelon et al.: (Alien Property Custodian) (published May 1943application filed January 1941).

McKay, H. B.: Air Ionizers, Radio-Electronics, July 1960 (pp. 32-33).

MILTON O. HIRSHFIELD, Primary Examiner.

SAMUEL BERNSTEIN, Examiner.

I. A. SILVERMAN, Assistant Examiner.

1. THE METHOD OF IMPROVING THE PROCESSING OF LOW MASS ARTICLES WHICH ARESUBJECTED TO ATTRACTION AND DISPLACEMENT BY ELECTRICALLY CHARGED BODIESCOMPRISING CIRCULATING ION CONTAINING ATMOSPHERE IN THE VICINITY OF SAIDLOW MASS ARTICLES IN A MANNER SO AS TO CONTACT AN OPPOSITELY CHARGEMEMBER WHICH CARRIES A CHARGE SUFFICIENT TO ANNIHILATE ATMOSPHERIC IONSBUT INSUFFICIENT TO GENERATE IONS THEREBY ANNIHILATING THOSE IONS WHICHWERE PREVIOUSLY CONTAINED WITHIN SAID ATMOSPHERE WHEREBY BODIES WILL NOTACQUIRE AN ELECTRICAL CHARGE SUCH AS TO SUBJECT LOW MASS ARTICLES TOATTRACTION AND DISPLACEMENT BY SAID ELECTRICALLY CHARGED BODIES.